How could he like me if he doesn't smile at me?

The guy I like shows a bit of the signs that he may like me as well. I've noticed he has done the whole staring and looking away when I look at him thing. I've especially noticed this when I'm with other guys (not even flirting just talking). He also is different towards me compared to everyone, including other girls. He can talk to any girl just fine but he seems to not talk to me at all. Almost as if he is nervous and tense around me. Even my friend said that she could tell that he was having trouble talking to me which made me feel bad because I really like him. The only time he didn't act like this around me was when he handed me his phone for more to add myself on his snapchat and he also put his arm around me and this other girl (the other girl has a bf and they're just friends). My friends say it's obvious he likes me and is afraid of embarrassing himself around me but the thing is he's never smiled at me before. I've heard that a guy who likes you will smile at least a little at you. This is why I get a vibe that my friends are wrong and that they're telling me this because that's what they think I want to hear and he actually doesn't like me. Guys, do you smile at girls you like? Is there a possibility that he may actually like me but just doesn't smile at me for some reason? Please help, thank you.
How could he like me if he doesn't smile at me?
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